Method and apparatus for bending metal to loop formation



April 22;.1947.

W. R. QYSTON METHOD AND APPARATUS FOR BENDING METAL TO LOOP FORMATION Filed March 15, 1943 5 Sheets-Sheet 1 April 22, 1947. w. R. OYSTON 2,419,418

METHOD AND APPARATUS FOR BENDING METAL 1'0 LOOP FORMATION Filed llarch 15, 1943 s Sheets-Sheet 2 v April 22, 1947. w. iQQOYSTON 2,419,418

METHOD AND APPARATUS FOR BENDING MEIAL TO LOOP FORMgTION 5 Sheets-Sheet 3 Filed March 15, 1943 l l l ul ql budl dl l b V l hur -1 5F450 I I April 22, 1947. w. R. OYSTON METHOD AND APPARATUS FOR BENDING METAL TO LOOP FORMATION Filed March 15, 1943 5 Sheets-Sheet 4 April 22, 1947. w. R. OYSTON 2,419,418

METHOD AND APPARATUS FOR BENDING METAL TO LOOP FORMATION Filed March 15,1943 5Sheets-Sheet 5 INVENTOR Patented Apr. 22, 1947 METHOD AND APPARATUS FOR BENDING METAL T LOOP FORMATION William Robert Oyston, Watford, England, as-

signor to Novobax Limited, Watford, England,

a British company Application March 15, 1943, Serial No. 479,178 In Great Britain January 29, 1942 9 Claims.

This invention relates to methods and apparatus for bending metal to loop formation.

One object of the invention is to provide an improved method of bending a substantially flat work-piece or blank into the form of a closed circular loop with the meeting edges in abutment.

More particularly the invention aims at providing an effective closure by abutment between the ends of a'strip of sheet metal bent to the form of a circular loop, the chief requirement being to ensure that with the particular metal employed the loop will be tightly closed (without overbending the metal by overlapping the ends of the loop) and remain so during and after such hardening, tempering or other heat treatment to which the article may have to be subjected.

Accordingly the invention provides a method of fabricating from a substantially flat workpiece or blank in strip or like form, a closed circular loop with the meeting edges in abutment, comprising the steps of wrapping the blank round a mandrel of oval, elliptical or similar elongated cross-section-whereof the major dimension approximates to the diameter of the circle required for the finished loop-to form a substantially closed loop conforming to the oval or like shape of the mandrel, and thereafter rotating the mandrel about a central axis while the blank is held (preferably resiliently) in an external die defining a boundary of circular configuration corresponding to the radius of curvature desired for the finished loop.

The invention includes a machine for carrying out the above method, comprising an external die constituted by two forming jaws of semi-circular cross-section located with the jaw openings opposed to one anodther and resiliently constrained towards one another, a mandrel of oval or like cross-section movable laterally (i. e. in a direction transverse to the axis of the forming jaws) into the nip between the jaws against the action of their resilient control,and means for rotating the mandrel about a central axis while situated as aforesaid in the nip between the jaws.

An important application of the invention is to the manufacture of ammunition feed link for usein the assembly of disintegrating feed belts such for example as are employed with the Browning machine gun. According to one design of such linkand the present invention i particularly concerned with the manufacture of this designeach feed link is fabricated from a blank in the form of a strip of sheet metal comprising a central portion and two oppositely offset end portions. The central portion is bent to form a tubular eye, hereinafter referred to as the main loop, and the end portions are bentin opposite directions away from-the central portion to form two spaced eyes which are smaller than the main loop and will hereinafter be re- 2 ferred to as the small loops. Each link thus takes the form of a figure 8 and the feed belt is assembled by locating the main loop of each link between the spaced small loops of the next adjacent link. The cartridge is carried by the small loops (one of which is smaller than the other) with which it makes a tight fit and is threaded through the main loop forming a pivot or hinge pin about which that loop may swing. In applying the present invention to the fabrication of feed links as described above, the method of forming a closed circular loop with the meeting.

edges in abutment is adopted for the formation of the main loop of the link. In this application of the invention the method comprises the successive steps of wrapping the central portion of the feed blank round an oval or like mandrel to form a main closed loop conforming to the shape of the mandrel, wrapping the end portions of the blank which extend beyond the main loop in opposite directions round mandrels appropriate to the dimensions of the small loops of the link, and thereafter rotating the main loop mandrel through at least while the main loop is resiliently held in an external die defining a boundary of circular configuration correspondin to the radius of curvature desired for the main loop.

The machine for carrying out the above application of the invention may comprise a slidof external forming jaws so located in successionin the path of advance of the block as to be embraced by the forked arms of the block when the latter is advanced, means for moving the forming jaws towards and away from one another,two mandrels carried by the sliding block in positions to co-operate in succession with the two sets of forming jaws, the leading mandrel being of oval cross-section appropriate to the formation of the main loop and the second mandrel being of a cross-section appropriate to the formation of the two small loops, means for moving the mandrels into, and retracting them from, the gap between the forked arms of the block, and means for rotating the main loop mandrel about a central axis.

A machine constructed and operating accord-. ing to the invention and adapted for the rapid manufacture of ammunition feed links of the design already referred to will now be described by way of example, and with reference to the accompanying drawings in which:

Figures 1 and 2 respectively are a plan and an elevation of one of the link blanks;

Figure 3 is a perspective view of the completed link;

Figures etc 9 are diagrams showing successive positions occupied by the link blank, the mandrels and the forming jaws during the forming operations;

Figure is a plan view showing the general arrangement of the machine, certain parts such as guards being omitted for the sake of clearness, and

Figures 11 to 13 are vertical sections showing successive positions occupied by the mandrels and associated parts.

Like reference numerals indicate like parts throughout the figures.

Each link blank is in the form of a sheet metal strip comprising a central portion 26 and two oppositely offset end portion 2 I, 22. The link blank is stamped out in a press, during which operation that end portion 22 of the blank which is to constitute the smaller of the two small loops is upset at 23 so that in the finished link the smaller of the two small loops will be in axial alignment with the companion loop. Also during the stamping operation the inner edge of the end portion 22 is slightly flared at 2 so as to facilitate the entry of the cartridge in the assembly of the feed belt. For the purpose of alignment and registration the two ends of the central portion 2% of the blank are formed respectively with a tongue 25 and a slot 26 so as to provide a keyed engagement at the abutment joint of the main loop. Further, during the stamping operation, the extremities of the end portions 2i, 22 are curved over slightly (as shown in Figure 2) in order to facilitate the formation of the small loops. During manipulation of the blank in the machine about to be described the central portion 20 is bent to form the main loo-p and the end portions 2|, 22 are bent in opposite directions away from the central portion to form the two small loops, that constituted by the portion 22 of the blank being smaller than that constituted by the portion 2|. As shown in Figure 3, the finished link takes the form of a figure 8.

The link-forming machine comprises a camactuated sliding block 2; carrying the mandrels for forming the main and small loops of the link and movable to and fro, in a rectilinear direction, into and out of a position in which the mandrels co-operate with pairs of spring-loaded forming jaws located insuccession in the path of advance of the block. Of the mandrels associated with the sliding block the leading mandrel 28 is of oval cross-section appropriate to the formation of the main loop. The sliding block Zl is in the form of a fork, the arms of which, in the advanced position of the block, embrace, with a clearance, the forming jaws. The leading mandrel 28 is a single plunger movable into and retractable from the gap between the forked arms of the block 2?. The mandrel 28 is provided at its outer endwith a collar 29 adapted to be engaged by one end of a rocker arm 3!! which is pivotally mounted on a bracket 3i carried b the sliding block 21 and which carries a roller 32 constituting a follower for a rocker arm operat ing cam 33 (of which a scrap View is shown in Figure 11). The second mandrel associated with the block 21 is in two plunger parts 34, 35 appropriate to the formation of the two small loops and movable from opposite sides respectively into and out of the gap between the forked arms. The small loop mandrels 3d, 35 are controlled by earn-operated sliding plates 36, formed with inclined slots 3'5, to engage pins 38 carried by the outer ends of the mandrels. Bodily reciprocation of the sliding block 21 is controlled by a cam 39 acting on a follower fit'carried by the block 21, and movement of the slotted plates 35 in relation to the sliding block 2'! is controlled by a cam 40 acting on a follower 9! (shown in Figures 10 and 13) carried by a crosspiece 56 which interconnects the slotted plates. The block 21 and the plates 38 are suitably guided for movement by appropriate portions of the machine structure. A shock absorber toil is provided between the crosspiece 56 and the follower 953.

The two pairs of forming jaws are constituted by two blocks ll, 2?. which are slidable in directions at right-angles to the path of the mandrelcarrying block 2? and are constrained by springs (see Figure 1G) in a direction towards one another. Each jaw block il, 52 provides two jaw elements, that is the corresponding side elements of the two pairs, the elements on the block as being identified as 34, 5 and those on block 22 as ll. The second pair of jaws 46, at (i. e. the second to be encountered in the advance of the mandrels) are of the proper radius to conform to the diameter required by the finished main loop. The first pair of jaws it, 45 have substantially the same dimensions as the second and with the first pair there is associated two pairs of supplementary jaws 59, 5| and 52, 53 appropriate in shape and dimensions to the two small loops. The supplementary jaws 5!], 51 are located in one plane which is above and parallel to the plane of the first pair of main loop-forming jaws ol, 55, while the supplementary jaws 52, 53 are in one plane which is parallel to and below the plane of the jaws 34, 35. The jaws 50, i i are shown in full lines in Figures 4 to 9 and the bottom supplementary jaws 52, 53 are shown in dotted lines in Figure 4 only. The actuation of all the jaws, main and supplementary, is controlled by cams $53 and 15 through rocker arms 5! which are pivoted at 32 and carry cam rollers 52. The outer ends of the rocker arms El operate the supplementary jaws 5t and 53 through spring-loaded bolts Q3. The supplementary jaws 52 and 5.! are operated by plates 94 which are ivotally mounted on the same axes 92 as the rocker arms 6i and engage the supplementary jaws 52, 5! by means of pins 95. The outer ends of the rocker arms 6i and the plates 94 are pressed inwardly by pre-loaded springs 15 operating through bars so which are connected to the outer faces of the plates 96 and bear on the corresponding outer faces of the arms 6|. The four supplementary jaws 58, 5! and 52, '53 are constrained towards the open or withdrawn position by means of light springs 91.

The method according to the invention proceeds in the following way. The link blanks are fed in succession to a position such that the middle of the central portion 20 of each blank in turn overlies the opening in the forming jaws. Any convenient feed mechanism may be employed, for example a reciprocating slide (not shown) fed from a magazine and operated by a push-rod 54 (Figure 10) movable to and fro with the sliding block 27. The relative positions of the blank, the forming jaws and the mandrels when the blank has been fed over the jaws are shown in Figure 4:, and the successive forming operations can best be appreciated by reference to the succeeding Figures 5 to 9. The zero posi tion of the machine is also illustrated in Figure 1.1 where the main loop mandrel 28 and the small loop mandrels 3 5, 35 are all clear of the. workpiece. Under the action of the earns 16 operating on the followers 62 the rocker arms 6| are adapted to be moved. into a position in which end portions 98 of the rocker arms engage flange por-' tions 99 at the ends of the jaw blocks M, 42 and these jaws.

aration, against the action of the springs 43. When the jaw blocks 4|, 42 are in this withdrawn position, i. e., that shown in Figure 4, the supplementary jaws 50, 5| and 52, 53 are similarly withdrawn to the maximum degree of separation by means of the light springs 91. Under the action of its operating cam 39 the sliding block 21 is advanced and at the same time the cam 33 operating through the rocker arm 30 allows the main loop mandrel 28 to be advanced laterally under the action of a spring (not shown) into a position between the forked arms of the block. In this way the main mandrel 28 is brought to bear on the central portion 28 of the blank and at the same time, immediately behind the mandrel, the reverse side of the blank is engaged by a spring-urged location punch 55 (see Figures 4 and 11) which exerts a resilient pressure on the blank holding it up against the main loop mandrel. Just as the mandrel 28 is advanced into a position between the forked arms of the block 21, the cams 16 release the rocker arms BI and the jaws 44, 45 and 46, 41 are moved, under the action of the springs 43, into their closed positions shown in Figure 10. On the continued advance of the sliding block 21 the blank is forced be tween the spring-loaded forming jaws and into the cavity of the first jaw opening 44, 45. By this operation the central portion 2|! of the blank is wound round the oval mandrel 28 and the two end portions are splayed in opposite directions as shown in Figure 5.

Under the action of their operating cam 40 the cam-plates 35 are now moved relatively to the sliding block 21 in the direction of travel of the latter. In consequence of this movement and by virtue of engagement in the inclined slots 31 on the cam-plates of the pins 38 at the outer ends of the small loop mandrels 34, 35, these mandrels are forced into the gap between the forked arms of the sliding block. This position of the small loop mandrels'is shown in Figure 12. The relative movement of the cam-plates 36 also has a further effect. The cam-plates are connected by a cross-piece 56 which carries a springloaded forming punch 51 located centrally between the forked arms of the sliding block. On relative movement as aforesaid of the slotted cam-plates, the forming punch 51 is brought to bear on the top of the main loop with the effect that the end portions 2|, 22 of the blank are further splayed apart and the top of the main loop is effectively closed. The action of the forming punch 51 in splaying apart the end portions 2|, 22 of the blank is practically simultaneous with the insertion of the small loop mandrels 34, 35. The form of the blank (the central portion of which is still of oval shape) when in this position is shown in Figure 6. The sliding block 21 continues its advance and the end portions 2 I, 22 of the blank are bent about the small loop mandrels as the block moves into its second position, as shown in Figures 7 and 13. This bending of the end portions 2|, 22 of the blank is effected by interference from the supplementary jaws '52, 5| on account of the positionsthen occupied by 7 Inthis position it will be seen that the main (1. e. oval) loop mandrel is between the second pair of forming jaws 46, 41 and the small loop mandrels are between the supplementary jaws 5|), 5| and 52, 53, with the punch 51 still bearing on the top of the main loop (but not shown in Figures 1 to 9 for sake of clearness). The cams 60 now come into action to control the closing in turn of the supplementary jaws 52, 5f

and 50, 53. The first action of the cams 60 is to permit, by initial movement of the rocker arms 8|, the bars to force (under pressure of the springs 15) the plates 94 inwardly, thus closing: in the supplementary jaws 52, 5| and bending:

over the ends 2|, 22 of the link to the positions shown in Figure 8. The next action of the cams 60 is to continue the movement of the rocker arms 6| (the plates 94 remaining stationary and merely continuing to apply spring pressure to the jaws 52, 5|) whereby the spring-loaded bolts 93 carried by the arms 6| drive in the supplementary (final) closure jaws 50, 53 by which means the small loops of the link are completed, this position of the parts being shown in Figure 9. The various cams are carried on a main driving shaft 88 of the machine. At this stage the main oval mandrel 23 is rotated about a central axis through This is effected by means of a chain 16 which is arranged to pass over a chain-wheel 1| mounted on the main loop mandrel 28 (Figures 10 and 11) and to have one end connected to a return spring 12 and the other end operatively coupled to a lever 13 which is actuated by a'cam 14 mounted on the main driving shaft 80 of the machine. In the initial operation of bending the blank about the oval mandrel 28 the metal at the base of the main loop is over-bent. On arriving at the second position in the forming jaws the central portion of the blank is of oval configuration, whereas the jaws between which it is accommodated are of cylindrical configuration, but on rotation of the mandrel it will be appreciated that the peaks of the oval iron their way inside the loop, thus forcing the blank into the correctly radiused jaws, bringing about local bending of the blank on each side of the. loop. In this way a tight abutment closure between the ends of the main loop is ensured-a closure which can be maintained in spite of any heat treatment to which the article may subsequently have to be subjected.

On completion of rotation of the main loop mandrel 28 as aforesaid, the forming jaws are opened, by means of the cams 16, cooperating with the cam rollers 62 on the rocker arms 6|. At the same time the main loop and small loop mandrels are retracted from their positions between the forked arms of the sliding block by the action of the control cams 33, 39, 40. Also on retraction of the cam-plates 35, which effects withdrawal of the small loop mandrels, the spring-loaded forming punch 51 is also withdrawn. The finished link is thereby cleared and is then discharged from the machine. The stripper block 8| (Figure 11) may be operated in order positively to ensure that the finished loop is thrown clear. The half-turn driving chain for the main mandrel is restored to its initial setting by its return spring, the mandrel-carrying block is returned to zero position (Figure 11), a fresh blank is delivered to the feed station over the forming jaws and the same sequence of operations is repeated.

The present invention is in no way limited to the constructional features of the machine described above. This description has been given solely for the purpose of illustration and it will be appreciated that there are many other applications of the invention (for example, to the formation of eyes on a hinge blank) in which the main principle of forming a closed circular loop by means of an oval or like mandrel may be embodied,

I claim:-

.1. A method of fabricating an ammunition feed link of the figure 8 type herein described, which comprises the successive steps of wrapping the central portion of thefeed blank round an oval or like mandrel to form a main closed loop conforming to the shape of the mandrel, wrapping the end portions of the blank which extend beyond the main loop in opposite directions round mandrels appropriate to the dimensions of the small loops of the link, and thereafter rotating the main loop mandrel through at least 90 while the main loop is resiliently held in an external die defining a boundary of circular configuration corresponding to the radius of curvature desired for the main loop.

2. A machine for fabricating ammunition feed links. comprising a sliding block in the form of a fork mounted for to and fro movement in a rectilinear path, two sets of external forming jaws so located in succession in the path of ad- Vancev of the block as to be embraced by the forked arms of the block when the latter is advanced, means for moving the forming'jaws towards and away from one another, two mandrels carried by the sliding block in positions to cooperate in succession with the two sets of forming jaws, the leading mandrel being of oval crosssection appropriate to the formation of the main loop and the second mandrel being of a crosssection appropriate to the formation of the two small loops, means for moving the mandrels into, and retracting them from, the gap between the forked arms of the block, and means for rotating the main loop mandrel about a central axis.

3. A machine according to claim 2 in which the leading mandrel is a single plunger movable from one side of the sliding block into and out of the space between its forked arms, and the second mandrel comprises two plunger elements appropriate respectively to the formation of the two small loops and movable from opposite sides of the block into and out of the space between'the forked arms.

4'. A machine according to claim 2 so operably arranged that the main loop is formed by movement of the sliding block to bring the leading mandrel into. a position between the first set of forming jaws, and that the small loops are partly formed by movement of the sliding block to bring the small loop mandrels into position between the first set of forming jaws, the main loop mandrel being at the same time advanced to a position between the second set of forming jaws.

5. A machine according to claim 2 so operably arranged that the main loop is formed by movement of the sliding block to bring the leading mandrel into a position between the first set of forming jaws, and that the small loops are partly formed by movement of the sliding block to bring the small loop mandrels into position between the first set of forming jaws, the main loo-p mandrel being at the same time advanced to a position between the second set of forming jaws, and that the formation of the small loops is completed by the action of supplementary jaw elements associated with the first set of forming jaws and camoperated in succession to close in the end portions of the link blank round the small loop mandrels. 6. A machine according to claim 2 so operably arranged that the main loop is formed by movement of the sliding block to bring. the leading mandrel into a position between the first set of forming jaws, and that the small loops are partly formed by movement of the sliding block to bring 5 the small loop mandrels into position between the first set of forming jaws, the main loop mandrel being at the same time advanced to a position between the second set of forming jaws, and a cam-actuated driving chain for rotating the main loop mandrel when it is positioned between the second set of jaws.

7 A machine according to claim 2 characterized by aspring-loaded location punch adapted to engage the rear face of the link blank behind the main loop mandrel, said machine being so operably arranged that the main loop is formed by movement of the sliding block to bring the leading mandrel into a position betweenv the first set of forming jaws, and that the small loops are partly formed by movement of the sliding block to bring the small loop mandrels into position between the first set of forming jaws, the main loop mandrel being at the same time advanced to a position between the second set of forming aws.

8. A machine according to claim 2 characterized by a front spring-loaded forming punch adapted to be driven against the. abutting ends of the main loop after the main loop mandrel has arrived in position between the first set of forming jaws, said machine being further so operably arranged that the main loop is formed by movement of the sliding block to. bring the leading mandrel into a position between the first set of forming jaws, and that the small loops are partly formed by movement of the sliding block to bring the small loop mandrels into position between the first set of forming jaws, the main loop mandrel being at the same time advanced to a position between the second set of forming jaws.

9. A machine according to claim 2 characterized by a front spring-loaded forming punch adapted to be driven against the abutting ends of the main loop after the main loop mandrel has arrived in position between the first set of forming jaws, and cam-actuated means for effecting the advance and withdrawal of the punch simultaneouay with the insertion and withdrawal respectively of the small loop mandrels, said ma- 50 chine being further so operably arranged that the main loop is formed by movement of the sliding block tobring the leading mandrel into a position between the first set of forming jaws,

and that the small loops are partly formed by 55 movement of the sliding block to bring the small loop mandrels into position between the first set of forming jaws, the main loop mandrel being at the same time advanced to a position between the second set of forming jaws.

WILLIAM ROBERT OYSTON.

REFERENCES CITED 5 The following references are of record in the file of this patent:

UNITED STATES PATENTS 

